NAV 2016 - Object of type CodeUnit with ID XXX could not be found

Hi,
I have a strange problem with a new NAV 2016 (CU6). If I try run own codeunit like CU 50000 with code MESSAGE('Hello'); I get always RTC message "Object of type CodeUnit with ID 50000 could not be found". Of course DEV licence for 2016.

I tried:
- restart RTC
- recompile all objects - some fails with not used addons (unknow variables for older version of dot net dll)
- sync with validate all
- restart server instance
- build server aplication objects
- renumber this CU
- export CU to fob, remove and import back
(Various combinations of this)

Event log at server or workstation nothing, just error message

It a little crazy/ghostly

First time a same CU worked.

Any ideas ??
Thx!